Mar. 2, 2007 Marni Rolston likes to think of herself as giving little massages to the sheep that lay on the table in front of her.
She isn't really massaging Sheep #17, but the thought is more pleasant than admitting she's using her bare fingers to spread its wool and look for lice, the Montana State University research associate said recently at the Fort Ellis Research Center near Bozeman.
Two crews working under spotlights were counting lice as part of an eight-week study sponsored by the Montana Sheep Institute at MSU. Researchers said an increasing number of Montanans are reporting the African blue louse in their sheep. The purpose of the study is to see if a chemical that kills lice on cattle is effective on sheep. The product contains an insecticide and insect growth regulator.
Heavy infestations of African blue lice can hurt sheep and pocketbooks alike, said Hayes Goosey, research scientist in MSU's animal and range sciences department and one of four researchers leading the study. Montanans who sell sheep lose money because the external parasite competes for nutrients. The sheep don't gain weight like they should, and ewes that carry too many lice can have anemia. If they're pregnant or nursing, they have less food for their lambs.
Growers who raise sheep for wool also lose money. The sucking lice remove more blood than they can digest, so they excrete the undigested blood and that stains the wool. The lice also break wool strands, which is a result of nutrient deficiency.
Jack Lloyd, another researcher on the project, said the African blue louse has been found on sheep in Wyoming, Idaho and Utah, as well as Montana. Therefore, the experiment will serve more than Montanans.
"All of these states will benefit," said Lloyd, professor emeritus at the University of Wyoming and a veterinary entomologist for 38 years.
Other researchers on the project are Greg Johnson, MSU professor of veterinary entomology, and Rodney Kott, MSU Extension Sheep Specialist. Helping them are others from Johnson's lab; Brenda Robinson, manager of MSU's Wool Lab; and Reid Redden, research associate with the Montana Sheep Institute.
The study started Jan. 16 and uses 32 Rambouillet sheep borrowed from a Montana producer, Johnson said. All the sheep were less than a year old. Separated from other sheep at Fort Ellis, the sheep in this project are divided into four groups of eight animals each. One group received no treatment for lice. A second group received the recommended treatment. The third group received double the recommended treatment. The fourth group received double the recommended treatment, but in a diluted form. Treatment involves applying a liquid chemical directly on the skin for about six inches along the sheep's back. The chemical then moves to other parts of the sheep's body through the wool.
The crew's first inspection, coming four weeks after the experiment began, showed that Sheep #17 carried only about five lice. At the beginning of the project, it had 21 lice. Sheep #17 was in the untreated group.
The report for another untreated animal was much different. The crew found 171 lice on a shoulder, 20 on a loin, 86 on the neck, 140 on the back and 930 on the rib area of Sheep #12. With hands starting to discolor from dried blood and excreted by-products, the crew ended up finding about 1,500 lice on one side alone. After flipping the animal and inspecting the other side, they reported 2,459 in all.
"We don't know a lot about the lice, how it's distributed over the animal, so we're looking at different parts of the body on both sides of each animal," Johnson said. This experiment hasn't been done anywhere before on the African blue louse, he added.
The crews counted lice on 32 sheep in one day and found their hands dirty, but amazingly soft from lanolin in the wool. They weren't worried about carrying lice home with them, because the lice are species specific, Johnson said. They won't jump onto humans. Besides being found on sheep, the African blue louse uses goats as a host in the southwest United States. Californians have also reported infestations on deer.
After four more weeks, the lice crews will inspect the sheep again, Johnson said. The experiment will then be finished. The researchers will analyze the results and tell the company that made the product if it can add sheep to its label. The designation would make it legal to apply the product on sheep.
The study was funded largely by Kott and the Montana Sheep Institute.
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